Wastewater treatment systems typically comprise one or more basins having essentially impermeable sides and bottom. One or more substrate layers such as soil, gravel, or synthetic media are placed on the bottom to support aquatic organisms such as bacteria, algae or the roots of aquatic plants. These systems have been used to reduce oxygen demand, suspended solids, pathogenic bacteria, and other wastewater constituents from domestic, industrial and agricultural wastewaters.
A reciprocating wastewater treatment system has two basins. Wastewater is introduced into one or both basins, and is then made to flow back and forth between the two basins. The frequency of the fill and drain cycle can be adjusted to control conditions for specific biotic and abiotic reactions such as nitrification, denitrification, sulfate reduction, and methanogenesis. Known reciprocating wetlands utilize pumps or airlift to move the liquid from one basin to the other, such as is disclosed in U.S. Pat. No. 5,863,433 to Behrends.